Rendering via python - markers problems
A quick easy way without scripting is to use the Outliner to disable render from cameras you do not wish to use.

If you specifically want to do it in script, you'll need to run through all objects of type 'camera' then set the value for those you wish to not to render.

bpy.data.scenes['Scene'].camera.hide_render=True

Render your scene then return the cameras.

Below seems to work fine but be sure to have your camera selected.

import bpy

list_of_all_scenes = bpy.data.scenes

if bpy.data.is_saved:
    for y in list_of_all_scenes:
        bpy.context.screen.scene = y
        selected = bpy.context.selected_objects
        objs = y.objects
        for x in objs:
            if x.type == 'CAMERA':
                x.hide_render = True
        objs.active.hide_render = False